[Bloat] Skype

[Ingemar Johansson S]

Hi

Been a year or so since I read about the inner secrets of Skype so this may be old..
I would suspect that your Skype session runs over TCP (via a Relay). This may happen e.g when a firewall blocks UDP. 
TCP (possibly in combination with a lossy WiFi connection) is what creates the high latencies. 

/Ingemar
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Message: 2
Date: Sun, 18 Nov 2012 15:57:53 +0100
From: Michael Welzl <michawe at ifi.uio.no>
To: bloat <bloat at lists.bufferbloat.NET>
Subject: [Bloat] Skype
Message-ID: <647D57F5-24CE-4006-AD2A-74141C84C3CB at ifi.uio.no>
Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes

Hi,

I have repeatedly noticed that Skype sometimes, in a long conversation involving video, can create massive audio delays (in the order of multiple seconds). This has happened to me in a conversation from a hotel room in the US to my home in Oslo (where, apologies, I haven't yet looked into de-bloating my modem and access point), and from my office in Oslo to someone else's office in the US.

I'm wondering: was that always due to bloated equipment along the path (including the end hosts), or does Skype poorly handle its internal buffers?

Any experiences? I suppose the way to find out is to run Skype over a verifiably de-bloated path. If, then, the problem never occurs, the fault is with the equipment and not with Skype (and vice versa).

Cheers,
Michael



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Message: 3
Date: Sun, 18 Nov 2012 08:09:03 -0800 (PST)
From: Alex Burr <ajb44.geo at yahoo.com>
To: bloat <bloat at lists.bufferbloat.NET>
Subject: Re: [Bloat] Skype
Message-ID:
	<1353254943.93761.YahooMailNeo at web126202.mail.ne1.yahoo.com>
Content-Type: text/plain; charset=us-ascii

I have noticed delays - although I don't think multiple seconds - but I think that it may be skype trying to make the best of a bad connection. I don't have any knowledge of the internals of the skype client, but I suspect that they take the view that delayed audio is better than incomprehensible audio - I think I have even heard it actually repeating the last bit of audio before a glitch, to give you a better chance to understand the next bit, and presumably catching up when the opportunity arises. 

So, an experiment to rule out skype might need to use not just a de-bloated path, but one with known packet loss.


Alex



----- Original Message -----
> From: Michael Welzl <michawe at ifi.uio.no>
> To: bloat <bloat at lists.bufferbloat.NET>
> Cc: 
> Sent: Sunday, November 18, 2012 2:57 PM
> Subject: [Bloat] Skype
> 
> Hi,
> 
> I have repeatedly noticed that Skype sometimes, in a long conversation 
> involving video, can create massive audio delays (in the order of 
> multiple seconds). This has happened to me in a conversation from a 
> hotel room in the US to my home in Oslo (where, apologies, I haven't 
> yet looked into de-bloating my modem and access point), and from my 
> office in Oslo to someone else's office in the US.
> 
> I'm wondering: was that always due to bloated equipment along the path 
> (including the end hosts), or does Skype poorly handle its internal buffers?
> 
> Any experiences? I suppose the way to find out is to run Skype over a 
> verifiably de-bloated path. If, then, the problem never occurs, the 
> fault is with the equipment and not with Skype (and vice versa).
> 
> Cheers,
> Michael
> 
> _______________________________________________
> Bloat mailing list
> Bloat at lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/bloat
> 


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